#include <bits/stdc++.h>
#define endl '\n'
using namespace std;

const int maxN = 100005;

int n, k, a[maxN], diff[maxN], sums[maxN], ans = INT_MAX;

int main()
{
    freopen("walk.in", "r", stdin);
    freopen("walk.out", "w", stdout);

    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    cin>>n>>k;
    for(int i = 0; i < n; i++)
    {
        cin>>a[i];

        if(i == 0) diff[i] = 0;
        else diff[i] = abs(a[i] - a[i - 1]);
    }

    for(int i = 0; i < n; i++)
    {
        sums[i] = (i == 0 ? 0 : sums[i - 1] + diff[i]);
    }

    for(int i = k - 1; i < n; i++)
    {
        if(sums[i] - sums[i - k + 1] < ans) ans = sums[i] - sums[i - k + 1];
    }

    cout<<ans<<endl;
    return 0;
}